The present invention relates to transmitters of the type used to measure process variables of industrial processes.
Process control loops are used in various industries to control or monitor operation of industrial processes. A process transmitter is typically part of the process control loop and is located in the field to measure and transmit a process variable such as pressure, flow or temperature, for example, to control room equipment. Some process control loops include a controller, such as a valve controller, which is controlled in response to the process variable sensed by the transmitter.
Process transmitters are frequently used in harsh, caustic environments or in environments which contain potentially explosive gasses or mixtures. Therefore, in order to reduce the possibility of damage to internal components of the transmitter from the caustic environment, and to reduce the possibility that internal circuitry causes an ignition of explosive gasses, the transmitter typically includes a transmitter housing which tightly seals the internal components. However, openings in the housing must be provided so that the transmitter circuitry can couple to external circuitry. To maintain a seal across these openings, each opening into the housing must be sealed using special isolation and blocking techniques. Each opening through the transmitter housing requires extra manufacturing steps and adds to the cost of the transmitter.